AWS Cloud Map

Protocol: JSON 1.1 Header: X-Amz-Target: Route53AutoNaming_v20170314.<Action> Endpoint prefix: servicediscovery

Floci emulates the AWS Cloud Map (service discovery) control plane in-process: namespaces, services, and registered instances are stored as account-aware domain objects, and discovery queries resolve against that in-memory state.

Asynchronous operations (CreateHttpNamespace, CreatePublicDnsNamespace, CreatePrivateDnsNamespace, DeleteNamespace, RegisterInstance, DeregisterInstance) apply their effect synchronously and return an operation id. The operation reaches SUCCESS immediately by default, so a follow-up GetOperation call returns a completed operation without polling. No Route 53 hosted zones are created: public and private DNS namespaces are assigned a synthetic HostedZoneId so SDK and CLI clients can exercise the full Cloud Map control flow locally.

DNS resolution

A DNS namespace is answerable, not just storable. Floci's embedded DNS server resolves <service>.<namespace> to the AWS_INSTANCE_IPV4 of the instances registered under that service, one A record each, so a container that uses Floci as its resolver reaches its peers by name. Instances registered directly through RegisterInstance and instances an ECS service registers through its serviceRegistries resolve the same way.

Which instances answer follows Route 53: the healthy ones while any instance is healthy, and all of them when none is, so a service whose instances have all gone unhealthy still resolves rather than disappearing from DNS. MULTIVALUE returns up to eight instances; WEIGHTED returns one randomly selected instance, with equal weights. Names inside a DNS namespace stay local when no instance has a usable address: the resolver answers negatively instead of forwarding them to upstream DNS. An absent service name receives NXDOMAIN; a service with registered instances and only other record types receives NOERROR with no A answers. DNS service names are unique without regard to case, as in AWS Cloud Map.

A and AAAA records use AWS_INSTANCE_IPV4 and AWS_INSTANCE_IPV6, respectively, and carry the TTL of the corresponding DnsConfig.DnsRecords entry. CNAME services answer with AWS_INSTANCE_CNAME, including when queried for A or AAAA. SRV queries return priority 1, weight 1, AWS_INSTANCE_PORT, and <InstanceId>.<service>.<namespace>. The SRV target also answers A and/or AAAA queries when those address attributes are registered, using the SRV TTL. The SRV service name itself has no address answer. Floci uses a 60-second fallback for older stored services without a usable A record TTL. New CreateService requests reject TTL values outside AWS's 0 to 2147483647 range. Names owned by Floci's embedded DNS server also use 60 seconds.

SRV registrations must produce an encodable DNS target: ASCII labels of at most 63 bytes and a full name of at most 253 characters. Floci returns InvalidInput before storing an unencodable target, rather than accepting a registration that cannot resolve. The API's general 64-character instance identifier limit is not a guarantee that an identifier can be used as a single DNS label; non-SRV registrations are unaffected. This early validation is an emulator behavior, not a verified claim about AWS's error timing. Older mixed A/CNAME configurations still resolve their explicitly configured A records.

UDP replies respect the legacy 512-byte limit or the client's EDNS payload size, capped at 4096 bytes. Oversized answers are truncated at whole-record boundaries and carry the DNS truncation flag. The embedded server remains UDP-only; TCP retry is not implemented.

Two limits are worth knowing. HTTP namespaces do not resolve, matching AWS, where they are reachable only through DiscoverInstances. The embedded DNS server only runs when Floci itself runs inside Docker, so name resolution is available to containers, not to processes on the host.

Supported Operations

Operation	Notes
`CreateHttpNamespace`	Creates an `HTTP` namespace; returns an operation id
`CreatePublicDnsNamespace`	Creates a `DNS_PUBLIC` namespace with a synthetic `HostedZoneId`
`CreatePrivateDnsNamespace`	Creates a `DNS_PRIVATE` namespace; requires `Vpc`, assigns a `HostedZoneId`
`GetNamespace`	Returns a namespace by `Id`
`ListNamespaces`	Lists namespaces in the current region
`DeleteNamespace`	Deletes an empty namespace; fails with `ResourceInUse` if it still has services
`CreateService`	Creates a service (optionally under a namespace), tracks revision and instance count
`GetService`	Returns a service by `Id`
`ListServices`	Lists services, optionally filtered by `NamespaceId`
`DeleteService`	Deletes a service with no instances; fails with `ResourceInUse` otherwise
`RegisterInstance`	Registers an instance under a service; requires `InstanceId` and `Attributes`, bumps service revision
`DeregisterInstance`	Removes a registered instance and bumps service revision
`GetInstance`	Returns a registered instance by `ServiceId` and `InstanceId`
`ListInstances`	Lists instances registered under a service
`GetInstancesHealthStatus`	Returns health status keyed by instance id, with optional `Instances` filter
`DiscoverInstances`	Resolves instances by `NamespaceName` + `ServiceName`, with `HealthStatus` and `QueryParameters` filtering
`DiscoverInstancesRevision`	Returns the current revision for a discovered service
`GetOperation`	Returns an operation by `Id`
`ListOperations`	Lists operations with optional `STATUS`, `TYPE`, `NAMESPACE_ID`, and `SERVICE_ID` filters
`TagResource`	Adds tags to a namespace or service ARN
`UntagResource`	Removes tag keys from a namespace or service ARN
`ListTagsForResource`	Lists tags for a namespace or service ARN

DiscoverInstances supports the HEALTHY, UNHEALTHY, HEALTHY_OR_ELSE_ALL, and ALL health filters, and matches instances whose attributes contain every key/value pair supplied in QueryParameters.

CloudFormation

Floci provisions these resource types:

AWS::ServiceDiscovery::HttpNamespace
AWS::ServiceDiscovery::PrivateDnsNamespace
AWS::ServiceDiscovery::PublicDnsNamespace
AWS::ServiceDiscovery::Service

Ref returns the namespace or service id. Fn::GetAtt exposes Id and Arn on all of them, HostedZoneId on a DNS namespace, and Name on a service.

Description, DnsConfig, HealthCheckConfig, and Tags update in place and keep the id. Only the TTLs in DnsConfig can change, as on AWS: an update that changes anything else in it, such as the record types or RoutingPolicy, fails with InvalidInput. A change to a createOnly property (Name, and Vpc on a private DNS namespace; Name, NamespaceId, Type, or HealthCheckCustomConfig on a service) replaces the resource: the new one is created and the old one is deleted once the stack update completes. As on AWS, a replacement that keeps the same name fails, since the name is still taken.

ServiceAttributes and Properties.DnsProperties.SOA are accepted but ignored.

Configuration

Variable	Default	Description
`FLOCI_SERVICES_CLOUDMAP_ENABLED`	`true`	Enable or disable the service
`FLOCI_SERVICES_CLOUDMAP_OPERATION_COMPLETION_DELAY_SECONDS`	`0`	Delay before an async operation transitions from `PENDING` to `SUCCESS`; `0` completes immediately

Examples

export AWS_ENDPOINT_URL=http://localhost:4566
export AWS_DEFAULT_REGION=us-east-1
export AWS_ACCESS_KEY_ID=test
export AWS_SECRET_ACCESS_KEY=test

aws servicediscovery create-http-namespace --name floci-demo

aws servicediscovery list-namespaces

aws servicediscovery create-service \
  --name backend \
  --namespace-id ns-xxxxxxxxxxxxxxxxxxxx

aws servicediscovery register-instance \
  --service-id srv-xxxxxxxxxxxxxxxxxxxx \
  --instance-id i-0123456789 \
  --attributes AWS_INSTANCE_IPV4=10.0.0.10

aws servicediscovery discover-instances \
  --namespace-name floci-demo \
  --service-name backend

import boto3

client = boto3.client(
    "servicediscovery",
    endpoint_url="http://localhost:4566",
    region_name="us-east-1",
)

ns = client.create_http_namespace(Name="floci-demo")
client.get_operation(OperationId=ns["OperationId"])  # Status == "SUCCESS"

namespace_id = client.list_namespaces()["Namespaces"][0]["Id"]
service = client.create_service(Name="backend", NamespaceId=namespace_id)

client.register_instance(
    ServiceId=service["Service"]["Id"],
    InstanceId="i-0123456789",
    Attributes={"AWS_INSTANCE_IPV4": "10.0.0.10"},
)

found = client.discover_instances(NamespaceName="floci-demo", ServiceName="backend")
print(found["Instances"])

Out of Scope

Route 53 hosted zone / record set creation.
Route 53 health checks backing HealthCheckConfig (custom health status is stored, not actively probed).
AWS_INIT_HEALTH_STATUS and AWS_EC2_INSTANCE_ID on RegisterInstance. Every instance registers HEALTHY, which is AWS's own initial status when AWS_INIT_HEALTH_STATUS is absent, so only a caller that explicitly asks for UNHEALTHY sees a difference.
Cross-region namespace and service discovery. A DNS query carries no region, so a name resolves through whichever namespace copy holds instances.